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and contains a cold saturated solution of sodium carbonate.
The anode is a wide strip of sheet lead. A current density of
6 to 9 amperes per 100 sq. cms. is passed for 17*4 ampere hours,
and then a lower current density for a further i2 ampere hours.
During the reduction the cathode liquid becomes very hot and
the alcohol which evaporates must be replaced. The cathode
liquid at the end of the process contains, in addition to azoben-
zene, azoxybenzene and hydrazobenzene. It'is poured into a
flask and the hydrazobenzene is oxidised to azobenzene by
aspirating a current of air through the solution for half an
hour. The greater part of the azobenzene separates and can be
filtered ; the remainder, which is less pure, is precipitated from
the filtrate by the addition of water. It is recrystallised from
ligroin. Yield 90 per cent, of the theory.
(Elbs, Electrolytic Preparations, trans, by R. S. Hutton,
p. 78.)
Hydrazobenzene (Diphenylhydrazine)C6H5N H. N H QH6
Alexejew, Zdtschr.f. Chein.,  1867, 33; 1868,497; E.Fischer,
Anleitung sur Darstdlung org. Praparate, p. 23.
50 grrns   (42 c.c.) nitrobenzene.
54          caustic soda (in 200 c.c. water).
50 c.c. alcohol.
100125 grms. zinc dust.
The apparatus is shown in Fig. 78. It consists of a1 large,
round, wide-necked flask (i-| litre) furnished with a cork perfor-
ated with three holes. Through one hole a stirrer, moved by a
water-turbine or electric motor, passes in the manner shown in
Fig. 78. To the stem of the stirrer a short, wide glass tube is
attached which revolves in the annular space formed at the end
of an adapter by fusing to it an outer concentric piece of wider
tubing. When this space is filled with water it serves as a
water seal. Through a second hole a wide glass tube is inserted
by which the zinc dust is introduced, and is fitted with
a cork. The third hole is furnished with an adapter to which
a condenser is attached. The nitrobenzene, caustic soda solu-
tion, and the alcohol are poured into the flask and the stirrer set